[Resolved] Buddypress pushes sidebar down – Platform theme

I installed the Platform theme of PageLines and installed the Buddypress plugin as well. Now, if I go to the pages of Buddypress on my website, the Sidebar is pushed down. It’s being showed underneath the content of Buddypress. Check http://www.voetbalspecialisten.nl/community/leden/ for example and you’ll know what I mean.

Not sure if this is the proper place to put this, been trying to navigate these forums for a while, and boy, I’m sure a newbie. But I have buddypress running with twentyeleven, ran the buddypress converter plugin as well, and created a child theme for twenty eleven. I’ve been making adjustments and so far everything is working alright except for the sidebar getting pushed down. I’ve tried to implement all kinds of options based on other answers I’ve read here and elsewhere, but so far nothing seems to work. Am I missing something obvious? Please help! For example it is happening on this page: http://inchelan.com/user-groups